The present invention relates to an improvement of heavy pneumatic tires for vehicles, and more particularly to pneumatic tires for use in trucks or buses designed to lessen catching of stones.
A main groove at the center of a plurality of grooves formed in a pneumatic radial-ply tire for heavy vehicle has been known to scarcely release catching stones when it is detached from the ground because the motion there is restricted by a metallic cord or the like. The stones are disadvantageously prone to be held in the groove and the tire catching the stones is damaged at the revolution. The damage is more and more propagated with the revolution of the tire.
In one proposal to avoid the aforementioned problem, the main groove, specifically, the side wall of the main groove is stepped or a platform is formed at the bottom face of the groove. Although the arrangement of this kind is effective to protect the bottom of the groove, it does not sufficiently work as a countermeasure to the catching of stones.
Naturally, the tire without any protection catches stones during running on a bad road, thereby inviting the breakage of the cord. The tire may be consequently impossible to reform.